Presently, various appliances and methods are used for the purpose of vacuum sealing plastic bags and containers to protect perishables, such as foodstuffs, and other products against oxidation. Conventional commercial appliances and some consumer appliances are generally expensive to manufacture, complex in construction and/or cumbersome to operate. There are also different types of heat sealing mechanisms contained in these prior art devices that have limited success in hermetically sealing the evacuated bags.
One type of conventional vacuum sealing appliances uses a vacuum nozzle that is inserted within a plastic bag for evacuation purposes. Although adaptable for low-volume home use, this type of system is cumbersome to use and normally requires a liquid separator or filter to prevent liquids or powders, retained within the bag, from being drawn into a vacuum pump connected to the nozzle. Further, a heat sealer employed therein must be closely synchronized with the positioning and withdrawal of the vacuum nozzle from the bag. This greatly adds to the cost and complexity of the device itself.
U.S. Pat. No. 3,928,938 discloses another type of vacuum sealing appliance that employs a heat sealing mechanism. In this appliance a user places a portion of a bag, containing a product to be packaged, in a first vacuum chamber and extends an open end or neck of the bag into a second vacuum chamber. The first vacuum chamber is then evacuated to expand the neck of the bag to isolate the chambers from each other. Then a vacuum is drawn in the second vacuum chamber to evacuate the bag. Thus, isolation of the two chambers from each other, during evacuation of the second vacuum chamber, is dependent on the physical properties composing the neck of the bag and very close synchronization and calibration of the evacuation and sealing procedures and controls therefore. This complex process in conjunction with the heat sealing mechanism is not reliable.
These prior art appliances described above and others require the use of special bags that must be purchased from the manufacturer. Due to the cost of the vacuum useable bags, it is desirable to conserve the material as much as possible. One problem with the above appliances is that there is a substantial amount of wasted vacuum bag material between the end of the bag and the heat seal as shown in Prior Art FIG. 12. FIG. 12 shows a container 20, with heat seals 21 and 22. For example, the vacuum sealed container 20 of FIG. 12 may be approximately 10 inches in length. The length between the end of the container 20 and each heat seal (21 and 22) is approximately an inch and a half. Therefore 3 inches of bag material is essentially unused for a 10 inch vacuum sealed bag. Therefore prior art devices waste approximately 30% of the vacuum bag material per use.
Another problem with prior art vacuum packaging appliances is that the temperature of the heat sealing mechanism is not accurately controlled. This is because the prior art appliances use a simple on/off time switch to excite the heat sealing elements. Under the heat seal control mechanism of the prior art, sealing multiple bags without allowing the heat sealing element to cool results in bags beginning to seal before the vacuum process is complete. This causes ineffective seals and prevents complete evacuation of gas from the bags, that results in expensive packaging bag waste. Further, activating the elements without considering real-time temperature may cause damage to the appliance due to element overheating.
Therefore there exists a need for a vacuum packaging appliance that accurately controls the temperature of the heat sealing elements and optimizes the placement of the heat sealing elements within the appliance.